The present invention relates to a flash lamp equipped with a mirror, utilized as a light source for spectroscopy, emission analysis or the like, a stroboscopic light source, a light source for processing high-quality images, or the like.
A conventional technique in such a field is disclosed in Japanese Patent Publication No. HEI 7-120518. In the mirror-equipped flash lamp described in the above-mentioned publication, a cathode and an anode are disposed facing each other inside a bulb made of glass, the front end of a trigger probe electrode is located between the cathode and the anode, and an inert gas, such as xenon or argon, is encapsulated in the bulb. Further, for attaining high-output light, an ellipsoidal mirror is disposed inside the bulb, and the cathode is inserted in an opening formed in the bottom part of the ellipsoidal mirror, whereby an arc emission point is formed at a first focal point inside the ellipsoidal mirror. By the provision of such an ellipsoidal mirror inside the bulb, a high-output flash lamp is produced.
Due to the above-mentioned configuration, however, the following problem exists in the conventional mirror-equipped flash lamp.
Namely, since the bottom part of the ellipsoidal mirror is formed with an opening, light reflected by the ellipsoidal mirror forms a dark portion in its irradiation area under the influence of the opening, thus lacking uniformity. As a result, when irradiation light is to be introduced into a small-diameter fiber or slit, there have been cases where shortages or inconsistencies in quantity of light occur. While Japanese Patent Publication No. SHO 56-50384 also discloses a xenon lamp equipped with a mirror, the mirror in this case is also formed with an opening for receiving a pedestal for supporting an electrode.
For solving the above-mentioned problem, it is an object of the present invention, in particular, to provide a mirror-equipped flash lamp adapted to generate uniform light whose irradiation inconsistencies are very small.
The mirror-equipped flash lamp in accordance with the present invention is a flash lamp in which an arc emission is generated by cooperation of a cathode, an anode, a trigger probe electrode, and a sparker electrode which are contained in an envelope having a light projection window, and this emission is emitted from the light projection window; wherein a mirror structure is fixed at an inner end portion of an exhaust pipe secured to a center of a stem disposed at a bottom portion of the envelope; the mirror structure comprising a mirror surface, contained in the envelope, facing the light projection window, and an exhaust path, formed at a position inside the mirror structure separated from the mirror surface, communicating an exhaust port of the exhaust pipe and the exterior of the mirror structure to each other.
In this mirror-equipped flash lamp, when a predetermined voltage is applied between the cathode and the anode, and a trigger voltage is applied to the trigger probe electrode and the sparker electrode, a discharge occurs at the trigger probe electrode and, along with this discharge, a main discharge of an arc occurs between the cathode and the anode. The resulting emission is reflected by the mirror surface, so as to be emitted from the light projection window. Such a mirror surface is formed in the mirror structure, which is fixed at the inner end portion of the exhaust pipe. However, since the exhaust pipe is utilized for letting out the air from within the envelope and introducing an inert gas into the envelope, it is not allowed to close the exhaust port of the exhaust pipe facing the interior of the envelope. Therefore, the exhaust path for communicating the exhaust port of the exhaust pipe and the exterior of the mirror structure to each other is formed inside the mirror structure, and is disposed at a position separated from the mirror surface, i.e., at a position not cutting out the mirror surface. As a result, the mirror surface can be made as a complete surface without opening a hole therein. Also, post-processing such as boring a hole in the mirror surface is not necessary, the whole mirror surface can be used effectively as a reflecting surface, and the reflection characteristics inherent in the mirror surface can fully be utilized.
Preferably, in this case, the mirror structure comprises a cup-shaped mirror holder having a bottom part fixed at the inner end portion of the exhaust pipe; a mirror body, mounted in an opening of the mirror holder, having the mirror surface at a top face thereof; a mirror body support surface, extending toward inside the mirror holder at a part of an inner wall face of the mirror holder, for supporting the mirror body; and the exhaust path formed between a bottom face of the mirror body and a bottom face of the mirror holder. When such a configuration is employed, the mirror structure comprises a mirror holder and a mirror body which are separated from each other and thus can be made of different materials, whereby the manufacturing cost can be cut down. Also, a simple assembling operation of exchanging mirror bodies with respect to the mirror holder can provide the mirror structure with a desirable mirror surface (e.g., rounded mirror, parabolic mirror, ellipsoidal mirror, polyhedron mirror, or the like). Further, making the mirror holder and the mirror body separate from each other is advantageous in that, since the mirror body is supported by the mirror body support surface such that the bottom faces of the mirror holder and mirror body do not come into contact with each other when the mirror body is mounted to the mirror holder, a space can positively be formed between the bottom faces of the mirror holder and mirror body, and this space can effectively be used as the exhaust path, whereby the exhaust path can easily be formed at a position separated from the mirror surface, i.e., at a position not cutting out the mirror surface. Also, as the exhaust path is disposed at this position, the exhaust port of the exhaust pipe and the exterior of the mirror structure can easily be communicated to each other. For example, a simple drilling process for only providing a side wall or bottom wall of the mirror holder with a hole communicating with the exhaust path can produce a gas port in the mirror structure.
Also, it is preferred that a mirror body fixing ring abutting against a peripheral edge in the top face of the mirror body and abutting against the inner wall face of the mirror holder be further provided. When such a configuration is employed, at the time of assembling the mirror structure, the mirror body can be constrained by the mirror body fixing ring as the latter is introduced into the mirror holder after the mirror body is mounted into the opening of the cup-shaped mirror holder, whereby the mirror body can be secured simply and reliably in the mirror holder.
Further, it is preferred that the mirror holder reduce its diameter on the bottom face side thereof at a part of the side wall thereof, so as to provide an inner wall face of the mirror holder with the mirror body support surface. When such a configuration is employed, at the time of assembling the mirror structure, even if the mirror body is simply mounted into the opening of the mirror holder, the bottom faces of the mirror holder and mirror body can be kept from coming into contact with each other, whereby the exhaust path can be secured easily.
Further, it is preferred that the mirror body be made of glass. When such a configuration is employed, in the forming of the mirror surface, the surface processing is easier than that in metals such as aluminum, thereby yielding a surface which not only can be made at a lower manufacturing cost but also has a low surface roughness and high surface precision. Also, when aluminum is vapor-deposited on a glass surface to form a mirror surface, a firm specular surface would be formed on the glass surface, whereby a highly durable mirror surface can be obtained.
Further, it is preferred that a gas port of the exhaust path is formed in a flat bottom wall of the mirror holder so as to penetrate therethrough. When such a configuration is employed, a drilling process for forming the gas port in the mirror holder becomes easy.
Further, the mirror surface preferably constitutes a rounded mirror. When such a configuration is employed, it is not necessary to form an opening at the bottom part thereof as in the case of an ellipsoidal mirror, whereby light-collecting efficiency can be improved.
Further, it is preferred that an arc emission part be disposed at a focal position of the mirror surface. Employing such a configuration in a rounded mirror enables the mirror surface to reliably collect light.
Also, it is preferred that the mirror structure comprise a block body, secured at the inner end portion of the exhaust pipe, having the mirror surface integrally formed at a top face thereof and the exhaust path therewithin. When such a configuration is employed, no additional step of assembling the mirror structure is needed, whereby the working efficiency of assembling the flash lamp would improve.
Further, it is preferred that, at a center of the block body in the bottom face thereof, a pipe insertion hole, extending in a center axis direction of the block body, for receiving the inner end portion of the exhaust pipe be provided, and that the exhaust pipe be secured to the block body with a screw. When such a configuration is employed, the assembling of the block body and the exhaust pipe to each other can be carried out easily and reliably.
Further, it is preferred that a gas port of the exhaust path be formed at a peripheral side face of the block body. When such a configuration is employed, a simple drilling process can communicate the pipe insertion hole and the exhaust path to each other at the time of forming the block body with the gas port.
Further, the mirror surface preferably constitutes a rounded mirror. When such a configuration is employed, it is not necessary to form an opening at the bottom part thereof as in the case of an ellipsoidal mirror, whereby light-collecting efficiency can be improved.
Further, it is preferred that an arc emission part be disposed at a focal position of the mirror surface. Employing such a configuration in a rounded mirror enables the mirror surface to reliably collect light.